Chain drive with idler wheel tensioning means biased by elongated pads

ABSTRACT

The chain drive has one run deflected and biased about a tensioning wheel which is mounted on a pivotal support. The support is, in turn, mounted on a pivot axis by means of an elongated tension spring element made up of a pair of concentric tubes and a resilient material between the tubes. The resilient material allows deflection of the support when an abrupt tension force is imparted to the chain as in the case upon braking.

United States Patent 1 1 1111, 3 7, Pfarrwaller June 18, 1974 CHAINDRIVE WITH IDLER WHEEL 1,982,299 11/1934 Hapgood 74/24211 R TENSIONINGMEANS E BY 2,087,253 7/1937 Herold 248/374 ELONGATED PADS 3,136,1706/1964 Murray 74/242.ll R 3,391,807 7/1968 Buschbom... 74/242.1 R 75 lt: Ew'nPf 'll ,W't th, I 1 or f,{, er er FOREIGN PATENTS OR APPLICATIONS1 380,671 9/1964 S t l d [73] Asslgneel g l f f Wmterthur, 413,4227/1934 01151 132 2311] 74/24211 B w1 zer an [22] Filed: Jan. 5, 1972Primary Examiner-Benjamin W. Wyche Assistant Examiner-Allan RussellBurke [21] Appl' 215590 Attorney, Agent, or Firm-Kenyon & Kenyon ReillyCarr & Chapin [30 Foreign Application Priority Data Feb. 5, 1971Switzerland 724/71 [57] ABSTRACT 52 us. (:1. 74/2421 R 74/24211 R TheChain drive has One deflected and biased [51] Int. Cl. Fl6h 7/12 about atensioning wheel which mounted on a 5s 1 Field ofSearch ..74/242.1511,2421 R, otal Support The Support is, in mounted a 74/242 1 119342;"i" 1f f *j3' pivot axisby means of an elongated tension spring ele- 7 2ment made up of a pair of concentric tubes and a resilient materialbetween the tubes. The resilient mate- [56] References Cited rial allowsdeflection of the support when an abrupt tension force is imparted tothe chain as in the case UNITED STATES PATENTS uponrbraking 622,5264/1899 Nies et al 74/240 1,045,875 12/1912 Nilsen 16/189 9 Claims, 7Drawing Figures CHAIN DRIVE IDLER WHEEL TENSIONING MEANS BIASED BYELONGATED PADS This invention relates to a chain drive and, moreparticularly, to a means for absorbing tension in the chain of a chaindrive. Still more particularly, this invention relates to a chain drivefor textile machines.

As is known, chain drives may be used, for example, to drive a dobbysuch as a cam or card dobby or to drive a Jacquard mechanism. Suchdrives may have to be abruptly stopped and re-started, for example, inthe event of yarn breakage, so that the chain has to take considerabletension duringsuch abrupt stopping and starting.

According to the present invention, a chain drive is provided with ameans to absorb the tension imparted to the chain. This means includes achain tensioning wheel situated on a pivotal support, and an elongatetorsion spring element situated between the support and the pivotal axisand extending in a direction parallel with the axis; The planecontaining the tensioning wheel substantially coincides with a centralplane perpendicular to the axis which passes through the center of thetorsion spring element.

The inclusion of the torsion spring element means that the chain doesnot have to take the considerable tension during abrupt stopping andstarting but can momentarily yield slightly while the chain tensioningwheel moves away from the chain. In the event of an abrupt tension beingimposed on the chain, the torsion spring element is stressed uniformlyon either side of the tensioning wheel and the central plane without anytilting.

Conveniently, the drive includes a chain deflector wheel which isconcentric with the axis. Thus, the direction of the chain run whicharrives at the deflector wheel is kept constant. The drive may include aslideway for the chain which is situated upstream of the deflectorwheel. In this way, the chain is prevented from rattling or undergoingany appreciable deflection due to vibration.

These and other objects and advantages of the invention will become moreapparent from the following detailed description and appended claimstaken in conjunction with the accompanying drawings in which:

FIG. 1 illustrates a first embodiment of a chain drive according to theinvention;

FIG. 2 illustrates a view taken on line ll-II of FIG. 1.

FIG. 3 illustrates a second embodiment of a chain drive according to theinvention;

FIG. 4 illustrates a view taken on line lV-IV of FIG.

FIG. 5 illustrates a third embodiment of a chain drive according to theinvention; and

FIGS. 6 and 7 illustrates views taken on lines VI-VI and VII-VII of FIG.5, respectively.

Referring to FIG. 1, a shaft 1 carries a driving sprocket wheel 2 androtates, for example, at the same speed as a main shaft (not shown).ofan associated loom. A sprocket wheel 5 mounted on a shaft 6 is driven inthe direction of arrow 4 via a roller link chain 3. A Jacquard mechanism(not shown) is driven from the shaft 6.

In order to absorb tension in the chain 3, a toothed chain tensioningwheel 7 is situated to mesh in one run 3a of the chain 3. The wheel 7 isrotatably mounted on 2 two bearing parts 9 (FIG. 2) between which aballor roller bearing 8 is disposed. The wheel 7 rotates about a spindle11 which is secured in: two parallel rocking arms 12 by means of a screwconnection 13.

Referring to FIG. 2, the rocking arms 12 form the support for the chaintensioning wheel 7. One end of each of the arms 12 is welded at 14 to anouter square tube 15 which encloses an inner square tube 16. Between thesquare tubes 15 and 16 are disposed four pads 17 of resilient material,for example, of rubber. Each pad 17 is elongated and is initiallydisposed to lie between a flat side of the tube 16 and a corner of theouter tube 15. The inner square tube 16 encloses a fixed spindle 19which is secured to a base plate 22 by means of a screw connection 21.At the right hand end of the spindle 19 (as viewed) a retaining ring 23is secured by a screw 24 so as to bear on the inner square tube 16. Thebase plate 22 is arranged to move on the machine frame 27 of anassociated Jacquard mechanism (not shown) by means of screws 25 andslots 26.

The parts 15, l6, l7 fonn a torsion spring element. As will be apparentfrom FIG. 2, the torsion spring element l5 17 extends longitudinallyoutwardly on both sides of the plane of the support arms 12 in parallelrelationship to the fixed spindle 19. A central plane 20 which passesthrough the center of the total length of the spring element containsthe plane of the chain tensioning wheel 7 and extends perpendicularly tothe spindle 19. Consequently, when the tensioning wheel 7 pivots asdescribed hereinbelow, the loading or stressing of the torsion springelement 15 17 and more particularly of the pads 17 is symmetrical anduniform on either side of the plane 20.

Referring to FIG. 1, the torsion spring element 15 17 is shown in atensioned (twisted) position. In this position, the element tends toturn the outer square tube 15 and hence the arms 12 in an anti-clockwisedirection as viewed back into the untensioned (untwisted) position inwhich the pads are disposed between the flat walls'of the inner tube 16and the respective corners of the outer tube 15. Consequently, the chaintensioning wheel 7 is continuously pressed against the chain run 3a. Ifthe Jacquard mechanism and the associated loom have to be stoppedabruptly,'for example, due to a weft or warp yarn breakage, themechanism and loom are braked and a force component 28 occurs in thechain 3 and momentarily urges the tensioning wheel 7 to the right asviewed. Under these conditions, the force exerted on the wheel 7 by thetorsion spring element 15 17 is temporarily exceeded and the wheel 7moves slightly to the right. When the instantaneous high braking forceon the chain 3 ceases, the tensioning wheel 7 is returned to the left tothe position illustrated as a result of the force exerted by the torsionspring element 15 17.

Once the yarn breakage in the loom has been cleared and the loom and theJacquard mechanism have been re-started there is an increased tension inthe chain 3, together with a force component 28 so that thereciprocating movement of the tensioning wheel 7 described above isrepeated.

Referring to FIGS. 3 and 4, wherein like reference characters indicatelike parts as above, rocking arms 12a are used as supports for thetensioning wheel 7 and the arms have projections 31 extending beyond thetorsion spring element. A stop formed from a square web 32 is situatedbetween the projections and a buffer 33 of resilient material, forexample, of rubber, is situated on the web 32. An arm 34 is alsosecured, for example by shrinking, onto the fixed spindle l9 and carriesan adjusting screw 35 at the free lower end. The screw 35 is situated ina screw-thread 37 which can be radially tightened by means of a screw36, and co-operates with the stop 32, 33.

The screw 35 serves to adjust the degree of prestressing of the torsionspring element 15 17. For example, referring to FIG. 4, the nut 21 canbe released and the tensioningwheel unit 7, 12a, 15 17, 34 can beremoved completely from the plate 22. The screw 36 is then moved topermit the screw 35 to be turned, for example, until the projections 31and the arm 34 are farther apart. The stress in the rubber pads 17 isthus increased. The screw 36 is re-tightened in a suitable position andthe tensioning wheel unit is fitted into the plate 22 and secured by thenut 21 in a position such that the chain wheel 7 is operative, withpractically no tension, simply to deflect the chain 3 as shown in FIG.3. The torsion spring element 15 17 is then pre-stressed. Only when thepull on the chain 3 increases, for example, during a sudden stopping orstarting, is the pre-stressing force momentarily overcome by theadditional force component 28 and the chain tensioning wheel 7temporarily pivoted in a clockwise direction as viewed in FIG. 3.

Referring to FIGS. to 7, wherein like reference characters indicate likeparts as above, rocking arms 12b are used which, as shown in FIG. 7,contain the stop 32 for the adjusting screw 35. The screw 35 is mountedin a projection 38 on a ring 39 secured on the fixed spindle 19.

The outer square tube and the inner square tube 16 of the torsion springelement 15 17 are split as can be seen in FIG. 6. A chain deflectingwheel 42 is rotatably mounted between the two parts of the inner squaretube 16 and between the wheel 42 and the two parts of the tube is aroller bearing 41. The chain run 3a passes through a slideway 43 whilethe run 3b passes through a slideway 44. The slideways preventtransverse movements of the chain due to vibration.

The effect of the deflector wheel 42 is such that the direction of thechain run 3a in the region of the slideway 43 remains constant if thetensioning wheel 7 is temporarily pivoted in the clockwise direction asa result of a sudden force component 28. Since the direction of thechain run upstream of the deflector wheel 42 is constant, the slideway43 can be used for this run of the chain although the pivotabletensioning wheel 7 is provided. The chain tensioning unit 15 17, 19, 7,41, 39 is screwed onto the base plate 22 by means of a tensioning ring46 and screws 47.

In all the embodiments, the plane containing the chain tensioning wheel7 coincides with the central plane of the torsion spring element 15 17.The chain tensioning wheel 7 is always mounted in the rock ing arms 12which are symmetrical with respect to the central plane 20; thearrangement is always such that the rocking arms 12 forming the supportare secured symmetrically of the central plane 20 on the outer squaretube 15 of the torsion spring element 15 17. The welding of the arms 12to the outer tube 15 maintains the symmetry and thus prevents anytilting of the tensioning wheel 7 in the event of sudden loading by thechain 3.

In a modified embodiment, a chain tensioner, for example, as in theembodiments described, may be pro vided on the chain run 3b so that twochain tensioners are provided. The tensioning wheel 7 may, if required,

be shifted slightly out of the central plane 20. Depending on the sizeof the components, the maximum amount for this is a few millimeters, andin any case must be such as to avoid any harmful unsymmetrical loadingand stressing of the torsion spring element 15 17.

The chain drive can be advantageously applied to machines other thentextile machines, particularly if increased tension occurs in a rollerlink chain 3 for a brief period during operation or if such increasedtension must be expected.

Other possible constructions are those in which the torsion springelement 15 17 is not pre-stressed. In that case, for example, as shownin FIGS. 1 and 2, the chain tensioning unit 15 l7, 7, 19, is screwed onto the base plate 22 by means of the screw 21 so that the chain run 3ais simply deflected and is practically unstressed by the tensioningwheel 7 during normal operation. When the increased tension occurs, forexample on stoppage, and when the tensioning wheel 7 is pivoted due tothe corresponding force component 28, there is no pre-stressing of thetorsion spring element 15 17 to be overcome so that even a relativelyslight force component 28 will temporarily pivot the wheel 7.

a toothed chain tensioning wheel rotatably mounted on said support forengaging a travelling chain; and

an elongated torsion spring element secured to said support about saidpivot axis and extending longitudinally outwardly on both sides of theplane of said support parallel to said pivot axis, said tensioning wheelbeing disposed in a central plane perpendicular to said pivot axis withsaid plane passing through the center of said torsion spring element,said spring element including a pair of concentric tubes and a pluralityof elongated pads of material between said tubes.

2. A chain drive as set forth in claim 1 which further includes a chaindeflector wheel rotatably mounted on said support concentrically of saidpivot axis for deflecting a travelling chain therearound.

3. A chain drive as set forth in claim 2 which further includes a chainslideway situated upstream of said deflector wheel relative to thedirection of travel of a chain passing therebetween.

4. A chain drive as set forth in claim 1 wherein said support is securedto the outer tube of said concentric tubes.

5. A chain drive as set forth in claim 1 wherein said support includes apair of arms situated symmetrically of said central plane.

6. In combination with a chain drive including an endless chain having apair of runs and means for driving said chain; means for absorbingtension in at least one of said runs, said means including a supportpivotally mounted about a pivot axis transverse to said support, atoothed tensioning wheel rotatably mounted on said support and engagingsaid one run, and an elongated torsion spring element secured to saidsupport about said pivot axis and extending longitudinally outwardly onboth sides of the plane of said support parallel to said pivot axis,said spring element including a pair of concentric tubes and a pluralityof elongated pads of resilient material between said tubes with saidsupport secured to the outer tube of said concentric tubes, saidtensioning wheel being disposed in a central plane perpendicular to saidpivot axis with said plane passing through the center of said torsionspring element.

7. The combination as set forth in claim 6 wherein outer tube of saidconcentric tubes.

1. A chain drive including a support pivotally mounted about a pivotaxis transverse to said support; a toothed chain tensioning wheelrotatably mounted on said support for engaging a travelling chain; andan elongated torsion spring element secured to said support about saidpivot axis and extending longitudinally outwardly on both sides of theplane of said support parallel to said pivot axis, said tensioning wheelbeing disposed in a central plane perpendicular to said pivot axis withsaid plane passing through the center of said torsion spring element,said spring element including a pair of concentric tubes and a pluralityof elongated pads of material between said tubes.
 2. A chain drive asset forth in claim 1 which further includes a chain deflector wheelrotatably mounted on said support concentrically of said pivot axis fordeflecting a travelling chain therearound.
 3. A chain drive as set forthin claim 2 which further includes a chain slideway situated upstream ofsaid deflector wheel relative to the direction of travel of a chainpassing therebetween.
 4. A chain drive as set forth in claim 1 whereinsaid support is secured to the outer tube of said concentric tubes.
 5. Achain drive as set forth in claim 1 wherein said support includes a pairof arms situated symmetrically of said central plane.
 6. In combinationwith a chain drive including an endless chain having a pair of runs andmeans for driving said chain; means for absorbing tension in at leastone of said runs, said means including a support pivotally mounted abouta pivot axis transverse to said support, a toothed tensioning wheelrotatably mounted on said support and engaging said one run, and anelongated torsion spring element secured to said support about saidpivot axis and extending longitudinally outwardly on both sides of theplane of said support parallel to said pivot axis, said spring elementincluding a pair of concentric tubes and a plurality of elongated padsof resilient material between said tubes with said support secured tothe outer tube of said concentric tubes, said tensioning wheel beingdisposed in a central plane perpendicular to said pivot axis with saidplane passing through the center of said torsion spring element.
 7. Thecombination as set forth in claim 6 wherein said spring element ispre-stressed to urge said wheel against said one run.
 8. The combinationas set forth in claim 7 wherein said means further includes an adjustingmeans for adjusting the amount of pre-stress of said wheel against saidone run.
 9. The combination as set forth in claim 6 wherein said springelement includes a pair of concentric tubes and a plurality of elongatedpads of resilient material between said tubes and said support issecured to the outer tube of said concentric tubes.